1. Field
The disclosed technology relates to electronic systems and, in particular, to phase-locked loops.
2. Description of the Related Art
Electronic parts, such as a synthesizer, can include a phase-locked loop (PLL). A PLL can be a closed-loop, frequency-control system based on the phase difference between an input clock signal and a feedback clock signal of a controlled oscillator. The PLL can generate an output signal having a phase related to the phase of an input reference signal. It can be desirable to detect that a PLL is locked in phase and/or frequency. In some instances, once the PLL lock has been detected, a processor can begin receiving and/or transmitting data.
Lock detection in existing PLL systems can be based on outputs of a phase frequency detector that is part of a feedback path of the PLL. This lock detection may be dependent on process, temperature, and/or a frequency at which the PLL is programmed. Any of these dependencies may cause lock detection to fail in a dynamic mode of operation. Alternatively or additionally, existing lock detection systems may detect a lock at a point later in time than the frequency is locked, due to the ways in which a lock is detected. Moreover, some existing lock detection can only predict frequency lock. Accordingly, a need exists for improved lock detection.